Bitmaps and Vectors

This tutorial is planned around using the pen tool in DrawPlus. It also applies to the pen tool in PhotoPlus that is used to create paths and selections (and any other software that uses Bézier curves). Attempting to make this tutorial as easy to follow as possible, any suggestions for improvement are welcome.

Before we start with the Pen tool and Bézier curves, it is important to understand the difference between bitmap and vector images because lines drawn with the pen tool fall into the vector category.

This is not a discourse on “vectors are better than bitmaps” (or vice versa) as each have their advantages and are better suited to some things than others. The context for this tutorial is to highlight how each works to gain a better understanding of the pen tool.

What do I mean?

Well, when the image was at its’ normal size the edges between the black curve and the background were reasonably sharp and smooth (if you were to magnify the original 100 x 100 square you would see that it is actually made up of tiny steps that blurred the blue background with the black line). As we increase the size we also increase that difference between the line and its’ background. We have added refinement to the line by what is called interpolation (basically the software makes up more of the ‘missing’ information to give us smoother transitions between pixels – some programs do a better job than others), so that is the guesswork we have added. But even interpolation cannot put in detail that was not there in the first place, therefore our line is more broken into by steps and its’ fuzziness has become more noticeable.

What of the vector curve?

This is the elegance and beauty of bézier curves. Still only one line needs to be written down! The scale box was ticked when the line was created so the line increased from 7.5 pt thick to 30 pt. It is only this information in the written line that would change. But the curve is still as pin sharp even when magnified three times.

Hopefully this will not to get too technical, please stick with it, as this is crucial for a better understanding that we will need later. Please scroll back to the image often to check what is being discussed.

We will start with the bitmap. Each pixel of an image carries information, not just on or off, but colour too. For every pixel, we must write down a value, each pixel's value is written down on a separate line – time to get out that bumper 240-page A4 pad! In our normal sized bitmap curve this equates to 100 x 100 lines of information - one line for every pixel (10,000 lines – we left these behind at school!).

Now we turn our attention to the vector curve. This has one line to plot every plot point, line and its’ angle between the points. There were two points and one line, so that is just one line of text, job done!

This difference becomes even more pronounced when we enlarge our two boxes. Each grows from 100 x 100 pixels to 400 x 400 pixels. Not only do we now need to write down a staggering 160,000 lines for the bitmap, we also have to make up the information contained in many of the lines as we go!

Conclusion

It is this difference between how the two file types (bitmaps and vectors) store information that has such a pronounced effect on file size and appearance. File size also has an effect on how long the processor takes to digest the file information, open and work on an image.

The basic way bitmaps (this includes jpeg images) store their information is with the 'building block' approach of pixels. The more a bitmap is enlarged (or zoomed into), the more these 'building blocks' are revealed. Vectors on the other hand store their information as a mathematical equation. The equation remains the same, no matter how much larger the image becomes or how closely it is zoomed into.

There is one more important thing to note about the difference between bitmaps and vectors following on from the way each file type works.

With the bitmap we can draw or paint any shape colour or object on the square in our example; the file size will remain the same, just the information stored on each line (one line for every pixel) will change. Because vectors are based on mathematical equations, more plot points and lines means more equations and a bigger file size (one line for every plot point, angle and line). This is best seen when using the brush tool in DrawPlus, as every brush stroke is a single vector line - it often takes many thousands of brush strokes to create a digital painting; resulting in a longer time processing the thousands of lines. DrawPlus has a number of excellent ways to ease congestion (a ‘flu medicine too?!!) and speed things up – an excellent subject for future tutorials as we want to keep things simple for now.

An explanation of how bitmaps and vectors work.

This also goes some way to explain the difference between the vector and bitmap fills. Vectors fill along the path from point a to b, resizing up only increases the path length whereas bitmaps, filling an area, sizing up reveals the building blocks.

Bitmap selection of the pen nib (above right) enlarged x1600

Vector selection of the pen nib (above right) enlarged x1600

Hopefully this has given you an insight to the difference between bitmaps and vectors. This information about vectors will be helpful as we move on to other tutorials for DrawPlus.

This image (please click on it to view at original size) shows bitmaps on the left and vectors on the right. The curves are identical; a bézier curve created with the pen tool has been copied, pasted and converted to a bitmap. You will notice they are both on semi-transparent boxes; this is solely to differentiate them from the background that shows grid lines. The boxes original size is 100 pixels square.

At the normal size, there is very little difference between the two. Enlarging both boxes to 400 pixels square there is a marked difference – the 3 x magnified sections highlight this difference. The bitmapped image shows an increased fuzziness (due to how bitmaps work) but the vector remains sharp.